The present invention relates to a surveillance system for recording images picked up by a surveillance camera.
In conventional surveillance systems aiming at crime prevention or the like, a long time recording VTR (video tape recorder) called time-lapse VTR is used in many cases. In such a time-lapse VTR, an image picked up by a surveillance camera or the like is recorded in a VTR in an analog form, for a long time or as occasion demands.
On the other hand, rewritable and re-recordable storage media, such as magnetic disks like hard disks and optical magnetic disks like MOs and DVD-RAMs, are spreading with larger capacities and inexpensive prices. Such storage media are easy in maintenance as compared with video tape for analog recording VTR. Furthermore, since immediate reproduction (random reproduction) is possible, such storage media tend to be used as recording media of time-lapse VTRS.
In conventional time-lapse VTRs, second, minute, o'clock, day, month, year of the time point when recording (image pickup) has been conducted are inserted in a picture for the purpose of image analysis at the time of reproduction as described in “CCTV surveillance system basic course” written by Masaaki Takahashi, and published by Industrial Development Organization Corporation, p. 89.
Furthermore, in order to facilitate retrieval of a desired image at the time of reproduction, such a scheme that supplement information is recorded simultaneously with an image picked up by a camera is disclosed in JP-A-9-46635.
In digital recording, an image picked up by a camera is typically subjected to image compression and then recorded. As a result, a larger quantity of images can be recorded. In JP-A-11-16059, there is disclosed such a scheme that an image picked up by a camera is compressed to JPEG and data of recording time is added to a header portion of JPEG.
In JP-A-11-103445, there are described a video recording device and a video editing device. In these devices, an MPEG video stream is generated from a video signal supplied from a camera. In addition, a subsidiary video stream is generated from bit map data of date and time information. The MPEG video stream and the subsidiary video stream are multiplexed and recorded. At the time of reproduction, display/non-display of the date and time information is switched over.